1. Field of the Invention
The invention relates generally to vehicle navigation and more particularly to a system for warning a driver when he or she is inadvertently changing lanes on a highway.
2. Description of the Prior Art
Many thousands of people are killed every year on highways as a result of a driver falling asleep at the wheel. With the driver asleep the vehicle drifts across lane boundaries creating an accident that often kills the driver, his passengers and sometimes people in other vehicles. Long distance truckers driving many hours in succession at night and others traveling great distances with little rest on rural freeways are especially at risk.
Several developments and proposals have been made for automatic guidance of vehicles along highway lanes that could potentially solve the problem of inadvertent lane changes due to falling asleep at the wheel. Most such systems use wires or magnets that are buried in the highway or have radio transmitters at very frequent intervals for triangulation. Unfortunately, the cost of the infrastructure for these systems has made large scale implementation unlikely or, at best, slow. Other systems have been developed or proposed using laser or sonar distance measurements to detect a vehicle ahead for use in avoiding rear end collisions. However, the laser and sonar measurements are not as well suited for detecting transverse motion such as an inadvertent lane change when no other object is adjacent.
Recently, improvements in differential global position systems (DGPS) have enabled DGPS receivers to obtain reliable near instantaneous sub-meter location accuracies with respect to a reference location. Conceivably, one could construct a conventional digital map database having highways mapped to sub-meter accuracy and then use the map database and conventional navigation techniques with a DGPS receiver in a vehicle for observing the vehicle position with respect to the highway. However, conventional map databases having such accuracy are time consuming and expensive to construct, and have very little other utility since sub-meter accuracy is not needed for normal highway navigation. There is a need for an inexpensive lane change alarm for warning a driver of an inadvertent lane change that does not require a new expensive highway infrastructure or a conventional precision map database.